"the dreadfully antiquated potestas patris familias"

   The legally enforced controlling authority held by a pater familias, the male leader of a Roman family, over its members and property.  At least in theory such a patriarch held the same powers over and responsibilities towards his family as the emperor bore over and towards Rome itself.  Appropriately for Freud's theories, children of such a family could not attain the role themselves until after their father's death.